1. Field of the Invention
The present invention relates to a piezoelectric component, such as a surface acoustic wave device or a piezoelectric thin film filter used in a delay line, a filter, other suitable component, and a method for manufacturing the piezoelectric component, and, particularly, to a chip-size packaged piezoelectric component and a method for manufacturing the chip-size packaged piezoelectric component.
2. Description of the Related Art
With compact and lightweight designs used in electronic apparatuses today, multi-function electronic components are required. Compact and lightweight design is also required for a piezoelectric component including a surface acoustic wave filter (hereinafter referred to as a SAW filter) and a piezoelectric thin-film resonator, which defines a surface acoustic wave device for use in communication apparatuses, such as cellular phones.
A piezoelectric filter includes piezoelectric resonators arranged in a ladder configuration or a lattice configuration. The piezoelectric resonator includes an Si substrate having one of an opening and a recess, and a vibrator disposed in the opening or the recess of the Si substrate and having a structure in which a thin film section, including at least one piezoelectric thin film layer (of ZnO or AlN), is sandwiched between at least a pair of opposed upper and lower electrodes with the top surface and the bottom surface of the thin film section respectively facing the upper electrode and the lower electrode. Alternatively, the piezoelectric resonator includes the Si substrate which does not have an opening or a recess, and the vibrator wherein space is arranged between the lower electrode and the Si substrate. Since such a piezoelectric filter uses vibration of a thickness-longitudinal mode generated in a vibrator, a vibration space must be provided and the vibrator must be protected from moisture and dirt.
The surface acoustic wave filter includes a pair of comb-like electrodes (interdigital transducers, hereinafter referred to as IDT) made of a metal, such as Al, and arranged on a piezoelectric substrate made of a crystal, LiTaO3, or LiNbO3. In the surface acoustic wave filter, a vibration space such as a propagation path of a surface acoustic wave of the IDT or the piezoelectric substrate must be provided and the IDT must be protected from moisture and dirt.
In the above-mentioned piezoelectric filter and surface acoustic wave filter, a die bond agent is applied to the bottom surface of a package made of a ceramic, such as alumina, elements of a piezoelectric filter and a surface acoustic wave filter are die bonded to the package, and terminals on the inside of the package are wire bonded to electrodes of the elements. The package is then encapsulated with a lid. To miniaturize the piezoelectric filter and the surface acoustic wave filter, electrode lands are disposed on the bottom surface of the package made of alumina, for example, the piezoelectric filter and the surface acoustic wave filter are mounted on the package using flip-chip bonding, and the package is then encapsulated with a lid.
Even if the piezoelectric filter and the surface acoustic wave filter are miniaturized in the above-described arrangement, a compact and low profile design cannot be implemented unless the package is miniaturized. Furthermore, miniaturized packages are costly. In the piezoelectric filter, in particular, the vibrator is disposed in the opening portion or a recess of the substrate. The vibrator is susceptible to damage due to an impact in a dicing step of the element or in pickup and die bond steps of the element during mounting of the element.
In contrast, elements are mounted using bumps as disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2001-94390), Patent Document 2 (Japanese Unexamined Patent Application Publication No. 11-150441), and Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2001-60642). According to these documents, flip-chip bonding is used to bond SAW elements to bumps provided on a base substrate, thereby eliminating the space required for wire bonding. Thus, the SAW filters are miniaturized. However, a conductive pad for a bump must be arranged on the SAW element, which reduces an effective area of the SAW element. Thus, miniaturization is difficult and the costs of producing bumps are incurred.
According to Patent Document 4 (Japanese Unexamined Patent Application Publication No. 2001-244785), a SAW element is mounted on a base substrate having a through-hole facing an extension electrode of the SAW element. An electrically conductive agent fills the through-hole, thereby forming an external circuit connection portion. The SAW filter is thus miniaturized.
In the arrangement disclosed in Patent Document 4, a SAW element and a base substrate are bonded together using a resin sealant. A corrosive component included in the resin, and moisture permeating the resin can corrode the IDT of the SAW element. With the IDT corroded, the performance of the SAW filter deteriorates.